A mixture was known to contain both KNO3 and K2SO3. To 0.681 g of the mixture, dissolved in enough water to give 50.00 mL of solution, was added 50.00 mL of 0.235 M HCl (an excess of HCl). The reaction mixture was heated to drive off all of the SO2, and then 25.00 mL of the reaction mixture was titrated with 0.159 M KOH. The titration required 11.13 mL of the KOH solution to reach an end point. What was the percentage by mass of K2SO3 in the original mixture of KNO3 and K2SO3